Electroplating rack



June 19, 1956 M. G. OSMAN ELECTROPLATING RACK 5 Sheets-Sheet 1 Filed May 24, 19 55 ATTORNEY June 19, 1956 M. G. OSMAN ELECTROPLATING RACK 3 Sheets-Sheet 2 Filed May 24, 1955 INVENTOR. 6: 04721612 ATTORNEY June 19, 1956 M. G. OSMAN ELECTROPLATING RACK S Sheets-Sheet 3 Filed May 24, 1955 IN VEN TOR. $6159]! 6'. 21711311 M BY ATTORNEY ELECTROPLATING RACK Mitchell G. Osman, Washington Township, Hendricks County, Ind., assignor to Radio Corporation of America, a corporation of Delaware Application May 24, 1955, Serial No. 510,779 8 Claims. (Cl. 204-297) This invention relates to a supporting rack for use in the electroforming of flat discs, and more particularly to an adjustable plating rack for selectively masking portions of the disc While the rack is submerged in a plating bath.

The general practice in the high speed plating of flat discs, such as phonograph record matrices, is to apply a preplate to a workpiece or disc which extends over the edges of the workpiece to form a clamp for holding the preplate to the workpiece. This clamping of the edges is particularly necessary in the manufacture of phonograph record matrices because it is necessary to separate the plate from the workpiece after the plating and electroforming has been completed. In order to facilitate this separation, the surface of the workpiece prior to plating is passivated or otherwise treated so that the plate itself will not adhere rigidly to the surface of the workpiece. One means of passivating a workpiece comprises oxidizing the surface to be plated which permits deposit of a readily removable plated layer. The preplating operation then is primarily concerned with providing a clamping plate about the edge of the workpiece which is sutliciently strong to maintain the plate in contact with the workpiece during the electroforming process, but which may be easily ruptured when the process is completed and it is desired to separate the plate from the workpiece.

After the desired preplate is formed, a plate of substantial thickness is electroformed over the preplate without increasing the thickness of the plate at the edge of the workpiece. Some means then must be provided to mask the edges of the workpiece after the preplating operation and during the electroforming operation.

In known practice the workpiece is placed in a rack which is in turn placed in a plating bath for the preplating operation. The workpiece is then removed and a rubber mask is fitted over the edge of the workpiece to prevent further plating at the edges. The workpiece is then again placed in a plating bath to provide an even electro-formed plate over the unmasked surface of the workpiece.

An object of this invention is to provide an electroplating rack wherein both the preplating and electroforming of a workpiece may be accomplished without removing the rack from the plating bath. Another object of this invention is to provide an adjustable electroplating rack wherein a workpiece is first held in a position for preplating and which is adjustable to mask or partially mask a portion of the workpiece for the electroforming.

A rack in accordance with the present invention for accomplishing these and other objects includes a rack base comprising a disc-like portion having a supporting extension and two masking members. A pair of contact plates are provided on each side of the rack base and are electrically connected to a conductive hook at the end of the supporting extension. A plurality of locking or atent C Patented June 19, 1956 spacing cams are provided on each side of the base around the periphery of the disc portion. These cams engage corresponding projections around the periphery of each masking member and serve to support the masking rings and to secure the masking rings and the workpiece against the rack base. Each of the masking rings may assume two positions within these cams each of which is a different fixed distance from the surface of the rack base. The transition between these two positions is accomplished by the rotation of the masking ring in relation to the rack base.

The novel features of the invention, as well as additional objects and advantages thereof, will be understood more fully from the following description when read in connection with the accompanying drawings, in which:

Figure 1 is a view in front elevation of a rack base;

Figure 2 is a view in elevation of a masking member looking at the side of the member which is adjacent the rack base;

Figure 3 is a view in front elevation of a rack assembly illustrating alternative positions of the masking member;

Figure 4 is a view in side elevation, and partially in section taken along the line 4-4 of Figure 3 looking in the direction of the appended arrows;

Figure 5 is an enlarged fragmentary sectional view taken along the line 55 of Figure 3 looking in the direction of the appended arrows and illustrating the operation of a locking cam;

Figure 6 is a view in side elevation, partially broken away, of an alternative form of rack assembly;

Figure 7 is an enlarged fragmentary sectional view taken along the line 77 of Figure 6 looking in the direction of the appended arrows and illustrating the operation of a locking cam;

Figure 8 is a fragmentary sectional view taken along the line 8-8 of Figure 6 looking in the direction of the appended arrows illustrating a means for securing the matrices to the rack base; and

Figure 9 is a view in side elevation, partially broken away, of another alternative form of rack assembly.

Referring now in more detail to the accompanying drawings, the present invention is set forth herein, illustratively, as a rack for the preplating and electroforming of phonograph record matrices. In one process of manufacturing phonograph records, the recording iscut on a lacquer disc from a magnetic tape recording. The lacquer is coated with a conductive material and the surface of this material is electroplated to provide a master which is a negative impression of the lacquer. The grooved surface of the master is then passivated and this is in turn electroplated to form a mold which is a positive reproduction of the lacquer. The grooved surface of the mold is then passivated and in turn electroplated to form a stamper which is again a negative reproduction of the lacquer. The stamper is the member which is fitted to a molding press and which presses the phonograph record discs. The masters, the molds and the stampers are all-metal members and are all described as matrices in the record making process. The racks in accordance with the present invention may be used for producing a mold from a master and for producing a stamper from a mold.

Referring now to Figures 1 through 5, the rack assembly consists essentially of three portions, a rack base 11 and a pair of identical masking rings 41 which are se cured to either side of the rack base. The rack base is composed of two identical portions of a sheet material having the configuration of a circular disc 13 with a handle 15 extending radially from the center of the disc. These sheet portions are composed of an insulating material such as a plastic, for example. Alternatively the rack base may be a one piece molded member. A pair of circular conductive plates 17 are attached to either side of the rack base at the center of the disc portion 13. These plates are of a fixed thickness and extend a fixed distance from the surfaces of the base 11. A centering pin 18 is provided on each of the plates 17. An elongated conductive strip 19 is positioned within the base 11 and extends from the circular plate 17 through the handle 15 and beyond the end of the handle where it is formed into a hook 21 which provides the means for supporting the rack assembly and also for carrying current to the plates 17. The conductive strip 19 is completely enclosed within the rack base and handle except for the exposed hook 21.

Three identical locking cams 2'7 are secured at equally spaced points around the periphery of the disc portion 13 of the rack base 11 on each side of the base. Looking at a face of the base 11, these locking cams 27 are arcuatc in shape, the outer edges of the cams being mounted contiguous the edge of the disc portion 13. The inner edges of these cams define a circle which is slightly larger than the diameter of the record matrices which are held in the rack. Referring now especially to Figure each of these earns 27 is provided with an extension 29 having an external surface 30 at the clockwise end of the cam and an internal cam surface 31 at the counterclockwise end of the cam. The extension 29' is an extension of the under surface of the cam 27 and is of a fixed thickness. The surfaces 30 then define a supporting plane parallel to the base 11 'at a fixed distance from the base. An inclined cam surface 33 extends from the end of the cam extension 29 to the upper surface of the cam extension. The internal cam surface 31 faces the surface of the disc 13 and is inclined with respect to this surface. While the outer surface 30 of the extension 29 extends completely across the face of the cam, the internal cam surface 31 extends from the inner edge of the cam only partly across the cam width.

Each masking ring 41 comprises a flat ring 43 having a circular inner periphery and having an irregular outer periphery comprising radial extensions or flanges 45 and 47. The ring 43 is provided with a handle 49 which cxtends radially from the center of the ring. A shield 51 is mounted concentrically with the masking ring 41 and is separated from the masking ring by three shield support members 53 which maintain the shelding ring a fixed distance from the masking ring.

Three flanges 45 are equally spaced about the ring 43 and the outer edges of these flanges define a circle whose diameter is substantially the same as the diameter of the disc 13. Three intermediate flanges 47 are equally spaced about the ring 43 and extend from the counterclockwise end of the flanges 45 in Figure 2 of the accompanying drawings. The opposite face of the masking ring 41 is illustrated in Figure 3. The outer edges of the flanges 47 define a circle whose diameter is somewhat greater than the diameter defined by the inner edges of the earns 27. The flanges 47 are adapted to engage the internal cam surfaces 31 of the locking cams 27. The smallest diameter of the masking ring 41, defined by the portions of the ring between the flanges 45 and 4-7, is slightly smaller than the diameter defined by the inner edges of the locking earns 27 to permit assembling of the masking rings 41 to the base 11.

A matrix 63, which is held within the rack, is provided with an aperture 64 at the center thereof. This aperture is adapted to receive the pin 18 to provide for concentricity of the matrix with the rack. After a matrix 63 is placed in the rack, a masking ring 41 is placed on the rack and is rotated to the preplating position in which the masking ring handle 49 is aligned parallel the base handle 15. The preplating. position is illustrated in Figure 3 as the full line position of the near masking ring. In this position, the flanges 45 are in engagement with the extensions 29 of the locking earns 27. The masking ring 41 is held away from the surface of the rack base 11 a certain distance determined by the thickness of the extensions 29. At the same time the flanges 47 are held under the locking earns 27 in engagement with the internal cam surfaces 31. The matrix 63 which is now held between these members is lightly engaged at its outer periphery by the masking ring 41. This provides a sufficient pressure on the matrix to maintain the center of the matrix in engagement with the plate 17 whereby the matrix is electrically coupled to the plate 17, and the masking is not sufficiently complete to prevent the desired preplating of the matrix edges. The preplating position of the matrix 63 and the flanges 45 and 47 in reference to the earns 27 is illustrated in section in Figure 5. This position of the matrix and masking ring is further illustrated in the upper half of the assembly of Figure 4.

In the preplating position the masking ring 41 is not rigidly held by the locking earns 27. In order to hold the masking ring 41 against rotationv with respect to the base 11, a pin 65 is provided adjacent the outer end of the handle 15 which extends through the handle to project from either side thereof. Each of the masking ring handles 49 is provided with an aperture 67 which is adapted to receive the pin 65. The handle 49 is provided with suflicient resiliency so that it may be slipped over the end of the pin 65 to either engage or disengage the handle from the pin.

While the masking ring 41 is in the above-described preplating position, the preplating of the matrix takes place. When the preplating period has ended, the masking ring 41 is rotated in a clockwise direction to the electroforming position. This position of the parts is illustrated in Figure 3 as the dotted line position of the near masking ring and the far masking ring appears in the full line position. The flanges 45 then move off the cam extensions 29 permitting the masking ring to move toward the rack base. At the same time the flange extensions 47 are moved further into the locking earns 27 and the masking ring is urged inwardly toward the base surface by the internal cam surfaces 31. The masking ring 41 is rotated until it securely clamps the matrix against the rack base. The inclined internal cam surface provides the clamping effect. When clamping has been accomplished, the portion of the outer periphery of the matrix, which is in engagement with the masking ring, is masked against further plating and the electroforming process is completed over the exposed portion of the matrix.

In the electroforming position of the masking rings, the matrix is slightly bowed due to the fact that the circular plates 17 extend outwardly from the surface of the rack base. This position of the work disc is illustrated in the lower half of the assembly of Figure 4. The positions of the matrix 63 and the flanges 45 and 47 with respect to the cams 27 are illustrated by dotted lines in Figure 5.

In some plating operations, it is not necessary to completely mask the edge portion of the matrix after the preplating operation in order to prevent excessive plating on the matrix edge. In these cases it is sufficient merely to bring a masking ring sufiiciently close to the edge surface of the matrix to reduce the current density of the plating bath in this area and hence merely reduce the amount of plating in this area rather than prevent it completely.

Referring now to Figures 6, 7 and 8, an alternative form of plating rack in accordance with the present invention is illustrated. in this embodiment a rack assembly 81 comprises essentially the same elements and configuration as the plating rack described above. These elements are a rack base 81, base disc portion 83, base handle 85, contact plates 87 and locking earns 89. Masking rings 91 are identical to the masking rings already described. Each ring 91 comprises a ring portion 93 having flange extensions 95 and, also, intermediate flange extensions 97. A

shielding ring 99 supported by members 101 and a handle 103 is also comprised within the structure of each ring 91.

In this embodiment a matrix 105 is rigidly secured to the contact plate 87 and remains fixed with respect to the rack base 81. A threaded stud 107 is provided at the base 81 and extends from either side of the base. A center aperture 108 provided in the matrix 105 is slightly larger than the aperture 64 described above in connection with Figure 4 and which cooperates with the centering pin. The center aperture 108 is adapted to receive a tapered insulating washer 109 which seats itself Within the center aperture. A depression 111 is provided in the center of the contact plate 87. This depressionis large enough to accommodate the portion of the washer 109 which extends through the matrix. The matrix is then secured to the plate 87, through the washer 109, by means of an insulated nut 113, for example.

The locking cams 89 primarily perform a spacing function in this embodiment and are essentially the same as the locking cams previously described except that an additional thickness or plate is provided at the under surface of the cam or the surface which is contiguous the base 81. At the clockwise end of the cam 89, shown at the right in Figure 7, a cam extension 121 includes two external surfaces 123 and 125 which are separated by an external cam shoulder 127. The two surfaces 123 and 125 define two supporting planes parallel to the base 81 and hence two positions of the masking ring 91 in relation to the base 81. A cavity 129 formed as a result of the internal cam surface 131 is not adjacent the base 81, as in the previously described embodiment, but is separated from the base by a thickness which is equivalent to the thickness in the extreme portion of the cam extension 121. In other words, a surface 133 which faces the internal cam surface 131 lies in the same plane as the surface 125 of the cam extension 121. The distance which separates the plane of these surfaces 125 and 133 from the surface of the base 81 is fixed so that when a matrix 105 is secured to the contact plate 87, the distance between the outer surface of the matrix and the adjacent surface of the masking ring 91, which lies in the above mentioned plane, is a predetermined set distance, this distance being set to control the plating as desired. The positions of the flanges 95 and 97 with respect to the cams 89 are illustrated by dotted lines in Figure 7 for the electroforming operation. This position of the masking ring 91 is illustrated in the lower half of the assembly of Figure 6.

When the masking ring 91 is rotated counter-clockwise with respect to the base 81 the flanges 95 are supported on the upper surface extension 123 of the cam and the ring 91 is held within the cam through the engagement of the flanges 97 with the internal cam surfaces 131. This is the preplating position of the rack. In this preplating position the handles 85 and 103 will be aligned as in the previous embodiment. The preplating position of the flanges 95 and 97 with respect to the cams 89 is illustrated in section in Figure 7. This position of the masking ring 91 is further illustrated in the upper half of the assembly of Figure 6.

Referring to Figure 9, a modification of the plating rack of Figures 6, 7 and 8 is illustrated. In this embodiment, the surface of the masking ring 91, which is adjacent the surface of the base 81, is provided with a plurality of pins 135 equally spaced about and adjacent the outer periphery of the masking ring. These pins 135 extend a fixed distance from the surface of the'masking ring. They do not engage the matrix during the preplating operation but do engage the matrix lightly during the electroforming operation. These pins are desirable in operations where the separation between the masking ring and matrix is quite critical and to assure that this spacing will be uniform about the periphery of the matrix in the event that the matrix is warped.

What is claimed is:

1. In a plating rack comprising a base portion and a masking portion, said base portion presenting a surface for cooperation with said masking portion, a plurality of locking members spaced about the periphery of said base portion, each of said locking members in conjunction with said base portion providing two circumferentially spaced separated surfaces lying parallel with said base portion, an inclined shoulder joining said surfaces, said separated surfaces defining two supporting planes for said masking portion, each of said locking members having an internal cam surface inclined with respect to said base portion, a plurality of radial extensions spaced about the periphery of said masking portion, a plurality of other radial extensions spaced about the periphery of said masking portion, each of said internal cam surfaces of said locking members being engaged with one of said first named radial extensions, each of said other of said radial extensions being engaged with one of said separated surfaces of one of said locking members, means for rotating said masking portion with respect to said base portion, and means for locking said masking portion against rotation when said other of said radial extensions are engaged with said circumferentially spaced separated surfaces.

2. In a plating rack comprising a base portion and a masking portion adapted to be positioned adjacent a surface of said base portion, a plurality of locking cams spaced about the periphery of said base portion, each of said locking cams providing an external surface spaced from said base portion, an inclined shoulder joining said external surface and said base portion, said external surfaces of said plurality of locking cams defining a supporting plane parallel to said base portion, each of said locking cams having an internal cam surface inclined with respect to said surface of said base portion, a plurality of radial extensions spaced about the periphery of said masking portion, a plurality of other radial extensions spaced about the periphery of said masking portion, each of said internal cam surfaces being engaged with one of said first named radial extensions, each of said other of said radial extensions being engaged with one of said external surfaces, means for locking said masking portion when said other of said radial extensions are engaged with said external surfaces, means for rotating said masking portion with respect to said base portion, and said masking portion being locked against said surface of said base portion by said internal cam surfaces.

3. In a plating rack comprising a base portion and a masking portion adapted to be positioned adjacent a surface of said base portion, a plurality of spacing cams spaced about the periphery of said base portion, each of saidcams providing two external surfaces spaced from said base portion, an inclined shoulder joining said external surfaces, said external surfaces of said plurality of spacing cams defining two supporting planes parallel to said surface of said base portion, each of said spacing cams having an internal cam surface inclined with respect to said base portion, a plurality of radial extensions spaced about the periphery of said masking portion, a plurality of other radial extensions spaced about the periphery of said masking portion, each of said internal cam surfaces of said spacing cams beingengaged with one of said first named radial extensions, each of said other of said radial extensions being engaged with one of said external surfaces of said spacing cams, means for locking said masking portion against rotation when said external surfaces of said cams further from said base portion are engaged with said other radial extensions, means for rotating said masking portion with respect to said base portion, and said masking portion being locked against said external surfaces of said cams nearer said base portion by said internal cam surfaces.

4. In a plating rack comprising a base portion and a masking portion adapted to be positioned adjacent a surface of said base portion, a center contact plate on said base portion raised from said surface, means for securing a workpiece to said plate whereby it is positioned in a plane parallel said base portion, a plurality of spacing cams spaced about the periphery of said base portion, each of said cams providing two external surfaces spaced from said base portion, an inclined shoulder joining said surfaces, said external surfaces of said plurality of spacing cams defining two supporting planes parallel to said base portion, said supporting planes being spaced further from said base portion than the plane of said workpiece, each of said spacing cams having an internal cam surface inclined with respect to said base portion, a plurality of radial extensions spaced about the periphery of said masking portion, each of said internal cam surfaces of said spacing cams being engaged with one of said radial extensions, a plurality of other radial extensions spaced about the periphery of said masking portion, each of said other of said radial extensions being engaged with one of said external surfaces of said cams, means for locking said masking portion against rotation when said external surfaces of said cams further from said base portion are engaged with said other radial extensions, means for rotating said masking portion with respect to said base portion, said masking portion being locked against the external surfaces of said cams nearer said base portion by said internal cam surfaces, a plurality of pins mounted on said masking portion adjacent its periphery, and said pins being adapted to engage the periphery of said workpiece when said masking portion lies in said supporting plane nearer said base portion.

5. A supporting rack for electroplating and electroforming comprising a base having a supporting handle, said base presenting a surface having a center contact plate mounted thereon, a conductive supporting hook extending from said handle, means enclosed within said base and said handle electrically connecting said contact plate and said conductive hook, a masking ring positioned adjacent said surface of said base, a plurality of locking cams spaced around the periphery of said base, said locking cams and said base providing separated surfaces defining two parallel supporting planes for said masking ring, each of said locking cams having an internal cam surface inclined with respect to said base surface, a plurality of radial extensions spaced around the periphery of said masking ring, each of said internal cam surfaces of said locking cams being engaged with one of said radial extensions when said masking ring is positioned in either of said supporting planes, said masking ring being movable from one supporting plane to another upon rotation thereof with respect to said base, and said masking ring being locked by said internal cam surfaces when positioned in said supporting plane nearer said base.

6. A supporting rack for electroplating and electroforming comprising a base having a supporting handle, said base presenting a supporting surface having a center contact plate mounted thereon, a conductive supporting hook extending from said handle, means enclosed within said base and said handle electrically connecting said contact plate and said conductive hook, a masking ring positioned adjacent said surface of said base, a plurality of locking cams spaced around the periphery of said base, said locking cams providing surfaces defining a supporting plane parallel to said base surface for said masking ring, each of said locking cams having an internal cam surface inclined with respect to said base surface, a plurality of radial extensions spaced around the periphery of said masking ring, each of said internal earn surfaces of said locking cams being engaged with one of said radial extensions when said masking ring is positioned in said supporting plane and on said base supporting surface, said masking ring being movable from said supporting plane to said base surface upon rotation thereof with respect to said base, and said masking ring being locked by said internal cam surfaces when positioned against said base surface.

7. A supporting rack for electroplating and electroforming comprising a base having a supporting handle, said base presenting a surface having a center contact plate mounted thereon, means for securing a fiat workpiece to said contact plate, a conductive supporting hook extending from said handle, means enclosed within said base and said handle electrically connecting said contact plate and said conductive hook, a masking ring positioned adjacent said surface of said base, a plurality of locking cams spaced around the periphery of said base, said locking cams providing separated surfaces defining two supporting planes for said masking ring, said supporting planes being parallel to and spaced from said workpiece, each of said locking cams having an internal cam surface inclined with respect to said base surface, a plurality of radial extensions spaced around the periphery of said masking ring, each of said internal cam surfaces of said locking cams being engaged with one of said radial extensions when said masking ring is positioned in either of said supporting planes, said masking ring being movable from one supporting plane to another upon rotation thereof with respect to said base, and said masking ring being locked by said internal cam surfaces when positioned in said supporting plane nearer said base.

8. A supporting rack for electroplating and electroforming comprising a base having a supporting handle, said base presenting a surface having a center contact plate mounted thereon, means for securing a flat workpiece to said contact plate, a conductive supporting hook extending from said handle, means enclosed within said base and said handle electrically connecting said contact plate and said conductive hook, a masking ring positioned adjacent said surface of said base, a plurality of locking cams spaced around the periphery of said base, said locking cams and said base providing separated surfaces defining two parallel supporting planes for said masking ring, said supporting planes being parallel to and spaced from said workpiece, each of said locking cams having an internal cam surface inclined with respect to said base surface, a plurality of radial extensions spaced around the periphery of said masking ring, each of said internal cam surfaces of said locking cams being engaged with one of said radial extensions when said masking ring is positioned in either of said supporting planes, a plurality of pins spaced around the periphery of said masking ring, said masking ring being movable from one supporting plane to another upon rotation thereof with respect to said base, said masking ring being locked by said internal cam surfaces when positioned in said supporting plane nearer said base, and said pins engaging a surface of said workpiece when said masking ring is positioned in said supporting plane nearer said base.

References Cited in the file of this patent UNITED STATES PATENTS 741,274 Pritchard Oct. 13, 1903 2,368,749 Dowling Feb. 6, 1945 2,675,348 Greenspan Apr. 13, 1954 

2. IN A PLATING RACK COMPRISING A BASE PORTION AND A MASKING PORTION ADAPTED TO BE POSITIONED ADJACENT A SURFACE OF SAID BASE PORTION, A PLURALITY OF LOCKING CAMS SPACED ABOUT THE PERIPHERY OF SAID BASE PORTION, EACH OF SAID LOCKING CAMS PROVIDING AN EXTERNAL SURFACE SPACED FROM SAID BASE PORTION, AN INCLINED SHOULDER JOINING SAID EXTERNAL SURFACE AND SAID BASE PORTION, SAID EXTERNAL SURFACES OF SAID PLURALITY OF LOCKING CAMS DEFINING A SUPPORTING PLANE PARALLEL TO SAID BASE PORTION, EACH OF SAID LOCKING CAMS HAVING AN INTERNAL CAM SURFACE INCLINED WITH RESPECT TO SAID SURFACE OF SAID BASE PORTION, A PLURALITY OF RADIAL EXTENSIONS SPACED ABOUT THE PERIPHERY OF SAID MASKING PORTION, A PLURALITY OF OTHER RADIAL EXTENSIONS SPACED ABOUT THE PERIPHERY OF SAID MASKING PORTION, EACH OF SAID INTERNAL CAM SURFACES BEING ENGAGED WITH ONE OF SAID FIRST NAMED RADIAL EXTENSIONS, EACH OF SAID OTHER OF SAID RADIAL EXTENSIONS BEING ENGAGED WITH ONE OF SAID EXTERNAL SURFACES, MEANS FOR LOCKING SAID MASKING PORTION WHEN SAID OTHER OF SAID RADIAL EXTENSIONS ARE ENGAGED WITH SAID EXTERNAL SURFACES, MEANS FOR ROTATING SAID MASKING PORTION WITH RESPECT TO SAID BASE PORTION, AND SAID MASKING PORTION BEING LOCKED AGAINST SAID SURFACE OF SAID BASE PORTION BY SAID INTERNAL CAM SURFACES. 